[PATCH][Review Requested][Compilation Time]

[Nowicki, Tyler]

Hi,

This patch aims to improve compile time performance by replacing uses of SmallPtrSet in SelectionDAG with a new class called FlagVector. The SmallPtrSet is used for keeping track of SDNode pointers. For example, in DAGCombiner.cpp it is used to keep a track of each unique SDNode in the working list. Performing an insert into a SmallPtrSet causes it to loop over all entries to determine if the pointer has been stored before. This patch avoids this O(N) operation by given each SDNode a unique number that is then used to index into the FlagVector. Since a SelectionDAG is instantiated for each function, its FlagVector doesn't grow prohibitively large.

Although FlagVector may appear similar to SmallVector it differs slightly in the semantics of its array operator which will grow the vector to contain the SDNode index. Suggestions are welcome on potential reuses of SmallVector, however, it is very convenient to have an array operator which automatically grows the vector. We have another patch coming which uses the FlagVector in the same manner.

This patch is part of a series of compile time improvements. Although these were originally produced by our colleague Wan Xiaofei, our team consisting of preston.gurd at intel.com<mailto:preston.gurd at intel.com>; sriram.murali at intel.com<mailto:sriram.murali at intel.com> and myself, are assuming all responsibility for this work.

PLEASE REVIEW. Thanks!

Tyler Nowicki
Intel

Benchmark

Trunk

Numbering.SD

401.bzip2

74.21

72.34

403.gcc

73.88

72.01

429.mcf

72.80

71.22

433.milc

78.78

76.75

444.namd

94.73

93.37

445.gobmk

36.28

35.38

450.soplex

71.41

69.66

456.hmmer

86.80

84.78

458.sjeng

96.38

94.44

464.h264ref

87.61

85.93

470.lbm

68.95

67.97

471.omnetpp

89.07

86.91

bitmnp01

84.06

82.61

cjpegv2data6

59.70

58.42

idctrn01

40.18

39.08

libquake2

48.48

47.10

libquake_portable

63.54

62.03

libxcsoar

47.44

45.92

linpack

142.14

140.99

matrix01

24.75

24.11

nbench

108.04

106.59

tblook01

44.03

43.30

ttsprk01

39.23

38.23

Geomean

65.85

64.41




401.bzip2

100.00

102.59

403.gcc

100.00

102.60

429.mcf

100.00

102.22

433.milc

100.00

102.64

444.namd

100.00

101.46

445.gobmk

100.00

102.54

450.soplex

100.00

102.51

456.hmmer

100.00

102.38

458.sjeng

100.00

102.05

464.h264ref

100.00

101.96

470.lbm

100.00

101.44

471.omnetpp

100.00

102.49

bitmnp01

100.00

101.76

cjpegv2data6

100.00

102.19

idctrn01

100.00

102.81

libquake2

100.00

102.93

libquake_portable

100.00

102.43

libxcsoar

100.00

103.31

linpack

100.00

100.82

matrix01

100.00

102.65

nbench

100.00

101.36

tblook01

100.00

101.69

ttsprk01

100.00

102.62

Geomean

100.00

102.24


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